diff --git a/headroom/ccr/response_handler.py b/headroom/ccr/response_handler.py
index f81fe2236..af9241e82 100644
--- a/headroom/ccr/response_handler.py
+++ b/headroom/ccr/response_handler.py
@@ -379,7 +379,15 @@ class CCRResponseHandler:
                 "content": response.get("content", []),
             }
         elif provider == "openai":
-            message = response.get("choices", [{}])[0].get("message", {})
+            # Guard an empty/malformed ``choices`` the same way the Google branch
+            # below (and ccr/tool_calls.py) already do: ``response.get("choices",
+            # [{}])`` only falls back when the key is absent, so a present-but-
+            # empty ``choices: []`` (or ``[null]``) — which OpenAI-compatible
+            # gateways can send on a content-filtered/usage-only response — made
+            # ``[0]`` raise IndexError (or ``.get`` raise on a non-dict).
+            choices = response.get("choices")
+            first = choices[0] if isinstance(choices, list) and choices else {}
+            message = first.get("message", {}) if isinstance(first, dict) else {}
             return {
                 "role": "assistant",
                 "content": message.get("content"),
diff --git a/tests/test_ccr_response_handler.py b/tests/test_ccr_response_handler.py
index 2e850ac1b..d7278b9ab 100644
--- a/tests/test_ccr_response_handler.py
+++ b/tests/test_ccr_response_handler.py
@@ -719,3 +719,30 @@ class TestExtractAssistantMessage:
         assert message["role"] == "assistant"
         assert message["content"] == "Hello"
         assert message["tool_calls"] == [{"id": "123"}]
+
+
+class TestExtractAssistantMessageEdgeCases:
+    """Regression: `_extract_assistant_message` must not crash on an empty or
+    malformed OpenAI `choices` array (OpenAI-compatible gateways can send
+    `choices: []` or `[null]` on content-filtered / usage-only responses)."""
+
+    def test_openai_empty_choices_does_not_crash(self):
+        handler = CCRResponseHandler()
+        msg = handler._extract_assistant_message({"choices": []}, "openai")
+        assert msg == {"role": "assistant", "content": None, "tool_calls": None}
+
+    def test_openai_null_first_choice_does_not_crash(self):
+        handler = CCRResponseHandler()
+        msg = handler._extract_assistant_message({"choices": [None]}, "openai")
+        assert msg == {"role": "assistant", "content": None, "tool_calls": None}
+
+    def test_openai_absent_choices_does_not_crash(self):
+        handler = CCRResponseHandler()
+        msg = handler._extract_assistant_message({}, "openai")
+        assert msg == {"role": "assistant", "content": None, "tool_calls": None}
+
+    def test_openai_normal_choice_still_extracts(self):
+        handler = CCRResponseHandler()
+        resp = {"choices": [{"message": {"content": "hi", "tool_calls": [{"id": "1"}]}}]}
+        msg = handler._extract_assistant_message(resp, "openai")
+        assert msg == {"role": "assistant", "content": "hi", "tool_calls": [{"id": "1"}]}